Object.setPrototypeOf()

语法

Object.setPrototypeOf(obj, prototype)

参数

obj

要设置其原型的对象。.

prototype

该对象的新原型(一个对象 或 null).

描述

如果对象的[[Prototype]]被修改成不可扩展(通过 undefined)，则什么都不做。否则，该方法将obj的[[Prototype]]修改为新的值。

Object.setPrototypeOf()是ECMAScript 6最新草案中的方法，相对于 Object.prototype.__proto__ ，它被认为是修改对象原型更合适的方法

示例

var dict = Object.setPrototypeOf({}, null);

Polyfill

我们必须借助非标准的  

使用较旧的 Object.prototype.__proto__ 属性，我们可以很容易地定义Object.setPrototypeOf 如果它不可用：.

// 仅适用于Chrome和FireFox，在IE中不工作：
Object.setPrototypeOf = Object.setPrototypeOf || function (obj, proto) {
  obj.__proto__ = proto;
  return obj; 
}

附加原型链

通过  Object.getPrototypeOf() 和 Object.prototype.__proto__ 的组合允许将一个整个原型链附加到一个新的原型对象：

/**
*** Object.appendChain(@object, @prototype)
*
* Appends the first non-native prototype of a chain to a new prototype.
* Returns @object (if it was a primitive value it will transformed into an object).
*
*** Object.appendChain(@object [, "@arg_name_1", "@arg_name_2", "@arg_name_3", "..."], "@function_body")
*** Object.appendChain(@object [, "@arg_name_1, @arg_name_2, @arg_name_3, ..."], "@function_body")
*
* Appends the first non-native prototype of a chain to the native Function.prototype object, then appends a
* new Function(["@arg"(s)], "@function_body") to that chain.
* Returns the function.
*
**/

Object.appendChain = function(oChain, oProto) {
  if (arguments.length < 2) { 
    throw new TypeError('Object.appendChain - Not enough arguments');
  }
  if (typeof oProto === 'number' || typeof oProto === 'boolean') {
    throw new TypeError('second argument to Object.appendChain must be an object or a string');
  }

  var oNewProto = oProto,
      oReturn, 
      o2nd, 
      oLast;
      
  oReturn = o2nd = oLast = oChain instanceof this ? oChain : new oChain.constructor(oChain);

  for (var o1st = this.getPrototypeOf(o2nd);
    o1st !== Object.prototype && o1st !== Function.prototype;
    o1st = this.getPrototypeOf(o2nd)
  ) {
    o2nd = o1st;
  }

  if (oProto.constructor === String) {
    oNewProto = Function.prototype;
    oReturn = Function.apply(null, Array.prototype.slice.call(arguments, 1));
    this.setPrototypeOf(oReturn, oLast);
  }

  this.setPrototypeOf(o2nd, oNewProto);
  return oReturn;
}

使用

例子一：向一个原型附加一个链

function Mammal() {
  this.isMammal = 'yes';
}

function MammalSpecies(sMammalSpecies) {
  this.species = sMammalSpecies;
}

MammalSpecies.prototype = new Mammal();
MammalSpecies.prototype.constructor = MammalSpecies;

var oCat = new MammalSpecies('Felis');

console.log(oCat.isMammal); 
// 'yes'

function Animal() {
  this.breathing = 'yes';
}

Object.appendChain(oCat, new Animal());

console.log(oCat.breathing); 
// 'yes'

例子二：将一个基本类型转化为对应的对象类型并添加到原型链上

function Symbol() {
  this.isSymbol = 'yes';
}

var nPrime = 17;

console.log(typeof nPrime); // 'number'

var oPrime = Object.appendChain(nPrime, new Symbol());

console.log(oPrime); // '17'
console.log(oPrime.isSymbol); // 'yes'
console.log(typeof oPrime); // 'object'

例子三：给函数类型的对象添加一个链，并添加一个新的方法到那个链上

function Person(sName) {
  this.identity = sName;
}

var george = Object.appendChain(new Person('George'), 'console.log("Hello guys!!");');

console.log(george.identity); // 'George'
george(); // 'Hello guys!!'

说明书

浏览器兼容性

相关链接

• Reflect.setPrototypeOf()
• Object.prototype.isPrototypeOf()
• Object.getPrototypeOf()
• Object.prototype.__proto__